1. Field of the Invention
The invention relates to a method for reliably determining the temperature of the passenger compartment of a motor vehicle, in particular for controlling an air-conditioning system in the motor vehicle, in which a sensor which detects the temperature of the passenger compartment of a motor vehicle is ventilated by a fan motor, the fan motor being previously operated with another motor vehicle device which generates a noise.
2. Description of the Related Art
In control units for controlling air-conditioning systems in motor vehicles, NTC or PTC elements are used to measure the temperature of the passenger compartment of the motor vehicle. It is customary to suck in the internal air by means of a small, quietly running motor on which a blade wheel is mounted, and to ventilate the temperature sensor of the passenger compartment in this way. This fan motor runs as soon as, for example, the driver opens the vehicle door (U.S. Pat. No. 5,311,746) or an open signal of the central locking system activates the internal light or the stationary heating system and this is detected by the air-conditioning control unit. This means that the fan motor is already running before the ignition is switched on and continues to run for a certain time after the ignition has been switched off, in order to cool the temperature sensor of the passenger compartment. However, as soon as the drive motor of the motor vehicle is switched off, the noise nuisance from the fan motor is thought to be troublesome by the user of the vehicle. According to U.S. Pat. No. 5,311,746, the fan motor can also be switched on when the ignition is activated.